Photographed by Lauren Perlstein.We all know people who tend to take the bigger half of the cookie. Will they ever become more generous? Well, maybe. Science says they could be stuck with certain (selfish) personality traits for life.A University of Exeter study published in this month’s Animal Behavior focused on temperaments of mongooses (you know, the bigger cousins of meerkats) and found that selfless or selfish personalities last over the course of their lives. Researchers measured...